Nonisothermal crystallization kinetic studies on melt processed poly(ethylene terephthalate)/polylactic acid blends containing graphene oxide and exfoliated graphite nanoplatelets

Nonisothermal crystallization kinetics of poly(ethylene terephthalate)/polylactic acid (PET/PLA) (90/10 and 75/25 wt %/wt %) blend prepared by a melt mixing process in the presence of graphene oxide (GO) and exfoliated graphite nanoplatelets (xGnP) were investigated. The transmission electron microscope (TEM) results revealed that both the GO and xGnP were not inclined to the PLA phase, and the distribution of GO in the blend matrix was better than that of xGnP. The scanning electron microscope (SEM) results demonstrated that both the fillers showed compatibilizing effect and refined the morphology of PLA dispersed phase. The crystallinity and crystallization behavior of samples were studied by X-ray diffraction (XRD) and multiple cooling rate Differential scanning calorimetry (DSC), respectively. The results showed that the degree of crystallinity and crystallization rate of PET was reduced by blending with PLA. Inclusion of the fillers to the blend further reduced the crystallinity while the crystallization rate was increased. Analysis based on Hoffman-Lauritzen theory revealed that, compared to xGnP, the GO as a better nucleating agent could more effectively reduce lamella thickness and surface folding free energy of the nanocomposites. Crystallization kinetic studies by Jeziorny model revealed two levels of primary and secondary crystallization mechanisms for all samples. Moreover, activation energy of crystallization of the GO-containing nanocomposites was lower than that of xGnP-based systems. All the theoretical treatment and experimental results confirm that, compared to xGnP, the GO is more suitable filler and has stronger effect on enhancing the crystallization kinetic of the PET/PLA blends. (c) 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47569.